For "market mavens": Tor.com, run by the publisher of the same name, launched in 2008. Tor is the first major publisher that I know of to completely reimagine its website as a social network, with blog posts, original fiction and art, and comics. It is widely considered one of the best places to publish science fiction and fantasy these days, given its substantial profile and stellar (for fiction) pay rate: 25¢ a word up to 5000 words, less beyond that.